In the electronics industry, as products such as cell phones and camcorders become smaller and smaller, increased miniaturization of integrated circuit (IC) packages has become more and more critical. At the same time, higher performance and lower cost have become essential for new products.
Multiple die module designs have responded to the need for increasing the number of electronic devices, such as integrated circuits or memory dies, within smaller areas. Initially, dies or dies were connected in an unpackaged, bare form in a horizontal plane. More recently, the industry has begun implementing integration by stacking dies. Three-dimensional packaging of this type offers higher die density and less required interconnect density than two-dimensional multiple die substrates. Furthermore, stacking provides a dense die structure having the footprint of a one-die package, and obtaining thicknesses that have been continuously decreasing.
The primary practical limitation to the number of dies that can be stacked in a stacked die package system is the low final test yield of the stacked-die package. It is inevitable that some of the die in the package will be defective to some extent, and therefore the final package test yield will be the product of the individual die test yields, each of which is always less than 100%. This can be particularly a problem even if only two die are stacked in a package but one of them has low yield because of design complexity or technology.
As integrated circuit packages become smaller, it is also increasingly difficult to test each die separately, due to handling difficulties since the individual die are stacked with adhesive or spacer and in between on a substrate. Further, because the quality of the die cannot be determined, defects in the module can be found only after the module has been assembled.
As a result, the yield of the semiconductor module is lowered while its cost increases. For this reason, a need still therefore exists for a system allowing separate testing of each die package in an efficient manner while providing an efficient use of the limited amount of space. In view of the ever-increasing need to save costs and improve efficiencies, it is more and more critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.